Ohmic contacts to plasma etched n-Al _0.58Ga _0.42N

Plasma etching is required to expose n-Al _xGa _1-xN layers for bottom-emitting ultraviolet light emitting diodes grown on sapphire. However, etching can increase the difficulty of forming Ohmic contacts. X-ray photoelectron spectroscopy and cathodoluminescence reveal how the semiconductor changes with etching and help explain why it becomes more difficult to form an Ohmic contact. A V/Al/V/Au metallization has been investigated for Ohmic contacts to n-Al _0.58Ga _0.42N etched with a BCl ₃/Cl ₂/Ar chemistry. Increased V thickness and higher annealing temperatures were required to obtain a specific contact resistance of 4.7 × 10 ^-4 Ω cm ² for etched n-Al _0.58Ga _0.42N compared to optimized contacts on unetched films.